The cabins of moving automobiles need to be isolated from the jarring movements of their wheels, so that they will remain relatively stable even though the wheels are jarred by road irregularities. Buildings located in dangerous earthquake areas such as California and Japan are subject to destructive ground movements. Therefore, it would be desirable if the buildings could be made to remain stable and upright even though the ground beneath them jolts in different directions. As a result, a variety of suspensions and shock absorbers have been designed to meet these needs.
Most motor vehicle suspensions share a common configuration. U.S. Pat. No. 5,016,911 to Takehara et al. (1991) shows a typical motor vehicle suspension. It consists of an arm for locating the wheel relative to the vehicle body, a spring for supporting the weight of the body and absorbing the energy imparted to the wheel by the road, and a damping strut for dampening the motions of the wheel. Although widely used, this configuration requires separate locating, energy absorbing, and damping components. In addition, the pivot arm causes the wheel to move up and down along an arc, so that the tire cannot maintain optimum contact with the road surface. Furthermore, the suspension travel is quite short, so that it is inadequate for fully absorbing the effects of very large bumps and pot holes.
A greater variety of designs exist for building shock absorbers. U.S. Pat. No. 5,134,818 to Parera (1992) shows a shock absorber comprising a number of vertical spring rods arranged in a cylinder embedded in the foundation. The rods support the weight of the building, which compresses the rods so that they bow radially outwardly. When the ground moves downwardly during an earthquake, the rods will extend slightly as they straighten so that they maintain the stability of the building. However, this device has very limited travel, mainly in the vertical direction, so that it is capable of absorbing only very minor ground movements, and is not very effective for the main type of earthquake movement, which is horizontal.
U.S. Pat. No. 5,103,605 to Sul (1992) shows another building shock absorber comprising a number of coil springs for supporting a building and isolating it from vertical and lateral ground displacements. The springs are mounted in a box slidably disposed on a pan. The pan is attached to the ground, so that when the ground jolts laterally during an earthquake, the pan will be free to slide about horizontally under the box, so that the building will remain stationary. Relatively large vertical ground displacements can be absorbed by the long coil springs. However, this device lacks a damping mechanism, so that the springs can allow the building to oscillate even after the ground movements subside.
Another type of building shock absorber is shown in U.S. Pat. No. 4,235,317 to Maciejewski (1980). It comprises a series of telescoping tubes with spring loaded sealing gaskets. The tubes are filled with an energy absorbing medium for absorbing the energy of very strong shocks. Because of the telescoping design, this device can absorb large displacement vibrations. However, it is much like the damping strut commonly used in motor vehicles, so that it cannot support the static weight of an object by itself. Therefore, it must be used in conjunction with other mechanisms such as locating arms, springs, etc.
In conclusion, conventional motor vehicles suspensions offer limited travel, so that they are unable to absorb large irregularities on road surfaces. They also cause the wheels to move in vertical arcs, such that the tires cannot maintain optimum contact with the road. Furthermore, they require separate components for locating the wheels, absorbing impacts, and dampening vibrations. Existing building shock absorber designs either offer very limited travel, so that they can only absorb minor quakes, cannot absorb horizontal shocks, or lack damping mechanisms to prevent continued oscillations of the building after the end of an earthquake.